Perception and other cognitive functions such as planning, thought, and learning reflect processing of complex information by cerebral neocortex. The great expanse of brain issue that comprise the cerebral cortex is composed of iterated, local neuronal circuits the transform afferent information and distribute it other brain regions, forming larger distributed neural systems. Local cortical circuits are thought to contribute to adaptive sensorimotor behaviors by responding dynamically to changing demands of the external environment and of the brain's own internal representation of it. Neuronal assemblies are readily identified in the rodent somatosensory cortex, which contains groups of synaptically interconnected neurons, called 'barrels', that are related one-to-one to individual whiskers on the contralateral face. Each barrel performs an ongoing transformation of its afferent inputs that enhances spatial and temporal contrast. This transformation has been accounted for quantitatively by a computation model based on known or plausible features of local circuitry. The model, and the biological data from which it is derived, postulates the existence of synaptic interconnections between and among neurons having particular receptive field characteristics. The research plan will employ single-and multiple-microelectrode recordings in conjunction with controlled sensory stimulation or whisker-based behavior paradigms to investigate these functional inter-relationships. Specific hypotheses will be evaluated by quantitatively measuring the receptive field properties of pairs of neurons whose direct synaptic interconnections have been functionally characterized through analysis of the neurons' concurrently occurring spike activities. By examining cortical function at a level between the biophysics and synaptic physiology of individual neurons and the larger scale framework of linked cortical columns, the research will address important but as yet unresolved issues concerning the adaptive nature of cortical receptive fields, the interplay of serial and parallel processing operation, the dynamics of cortical information processing and the composition of local cortical network, including their size and interdigitation. Results will add significantly to understanding what local cortical network do and how they do it. Knowledge at this level of cortical function is essential for bridging the gap between cellular physiology and the eventual accurate diagnosis and treatment of perceptual/motor and other cognitive dysfunction due to nervous system disease or trauma.